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我有一个使用 Sherlock 操作栏的应用程序，我已经拆分了操作栏。单击操作栏中的下一个项目时，我正在尝试加载下一个 html 文件。但它告诉我错误。这是我的代码。

活动.java：

public class TutorialViewActivity extends SherlockActivity {

    // Tutorial No
    int TutorialNo;

    // progress dialog
    ProgressDialog mProgress;

    // Share String
    String copy;

    // String for URL
    String URL;

    // Settings Values - COMPLETED
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Check Settings
        settings();
        // Check Full Screen
        if (Fullscreen_Sett == true) {
            // hide statusbar of Android
            getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                    WindowManager.LayoutParams.FLAG_FULLSCREEN);

        }

        // orientation Settings
        if (Orientation_Sett.equals("Portrait")) {
            setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
        } else if (Orientation_Sett.equals("Landscape")) {
            setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);

        } else {
            setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR);
        }

        // showing layout
        setContentView(R.layout.tutorialview_layout);

        // Backlight ON/OFF
        if (Backlight_Sett == true) {
            getWindow()
                    .addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
        }

        // Getting Strings(level) From Main Activity
        Bundle extras = getIntent().getExtras();
        String TutorialName = extras.getString("TutorialName");
        TutorialNo = extras.getInt("TutorialNo");
        TutorialNo++;

        // Loading file html link
        URL = "file:///android_asset/Tutorials/" + TutorialNo
                + "/androidtutorial.html";

        String copy_share = "tutorials" + TutorialNo + "/copyshare.txt";
        // Getting Text for copy share
        try {
            copy = readTxt(copy_share);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        // ActionBar
        ActionBar ActionBar = getSupportActionBar();
        ActionBar.setTitle("CHAPTER " + " : " + TutorialNo);
        ActionBar.setSubtitle(TutorialName);
        ActionBar.setDisplayHomeAsUpEnabled(true);
        ActionBar.setHomeButtonEnabled(true);

        // method called for tutorialview
        tutorialview();

    }

    /************************************ SETTINGS ******************/
    public void settings() {
        // SETTINGS
        SharedPreferences SP = PreferenceManager
                .getDefaultSharedPreferences(this);
        Zoom_Sett = SP.getBoolean("zoomcontrols_settings", true);
        fitscreen_settings = SP.getBoolean("fitscreen_settings", false);
        Animation_Sett = SP.getBoolean("animations_settings", true);
        Fullscreen_Sett = SP.getBoolean("fullscreen_settings", false);
        Backlight_Sett = SP.getBoolean("backlight_settings", false);
        Orientation_Sett = SP.getString("orientation_settings", "Sensor");

    }

    // Method for tutorial view
    public void tutorialview() {
        // webview
        WebView wv = (WebView) findViewById(R.id.TutorialWebView);

        // webview settings
        WebSettings webSettings = wv.getSettings();

        // if (Orientation_Sett.equals("Portrait")) {
        // new webview
        wv = new WebView(this);
        // contentview of webview for progressdialog
        setContentView(wv);

        // the state of progress dialog
        mProgress = ProgressDialog.show(this, "Loading",
                "Please wait for a moment...");

        // add a WebViewClient for WebView, which actually handles loading
        // data
        // from web
        wv.setWebViewClient(new WebViewClient() {
            // load url
            public boolean shouldOverrideUrlLoading(WebView view, String url) {
                // setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR);
                view.loadUrl(url);
                return true;
            }

            // when finish loading page
            public void onPageFinished(WebView view, String url) {
                if (mProgress.isShowing()) {
                    mProgress.dismiss();
                }

            }

        });
        // }
        // Webview controls
        if (Zoom_Sett == true) {
            webSettings.setBuiltInZoomControls(true);
            wv.loadUrl(URL);
        } else if (fitscreen_settings == true) {
            webSettings.setBuiltInZoomControls(true);
            webSettings.setLoadWithOverviewMode(true);
            webSettings.setUseWideViewPort(true);
            wv.loadUrl(URL);
        } else {

            wv.loadUrl(URL);
        }
    }

    /****************************************************************************/

    // Dropdown Menu

    @Override
    public boolean onCreateOptionsMenu(com.actionbarsherlock.view.Menu menu) {
        getSupportMenuInflater().inflate(R.menu.tutorialview, menu);
        return super.onCreateOptionsMenu(menu);
    }

    /****************************************************************************/

    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    @SuppressLint("NewApi")
    @SuppressWarnings("deprecation")
    public boolean onMenuItemSelected(int featureId, MenuItem item) {

        int itemId = item.getItemId();
        switch (itemId) {
        // Home Back ActionBAr
        case android.R.id.home:

            onBackPressed();

            break;

        case R.id.copy:
            int sdk = android.os.Build.VERSION.SDK_INT;
            if (sdk < android.os.Build.VERSION_CODES.HONEYCOMB) {
                android.text.ClipboardManager clipboard = (android.text.ClipboardManager) getSystemService(Context.CLIPBOARD_SERVICE);
                clipboard.setText(copy);
                Toast.makeText(getApplicationContext(), "Coped To Clipboard",
                        Toast.LENGTH_SHORT).show();
            } else {
                android.content.ClipboardManager clipboard = (android.content.ClipboardManager) getSystemService(Context.CLIPBOARD_SERVICE);
                android.content.ClipData clip = android.content.ClipData
                        .newPlainText("", copy);
                clipboard.setPrimaryClip(clip);
                Toast.makeText(getApplicationContext(), "Coped To Clipboard",
                        Toast.LENGTH_SHORT).show();
            }
            break;

        case R.id.next:

            TutorialNo++;
            // Loading file html link
            URL = "file:///android_asset/Tutorials/" + TutorialNo
                    + "/androidtutorial.html";
            // method called for tutorialview
            //tutorialview();
             WebView wv = (WebView) findViewById(R.id.TutorialWebView);
            wv.loadUrl(URL);
            Toast.makeText(getApplicationContext(), "Next", Toast.LENGTH_SHORT).show();
        }

        return true;
    }// Home Back ActionBAr End

    // Reading TextFiles
    public String readTxt(String copy_share) throws IOException {

        InputStream inputStream = getAssets().open(copy_share);
        // System.out.println(inputStream);
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();

        int i;
        try {
            i = inputStream.read();
            while (i != -1) {
                byteArrayOutputStream.write(i);
                i = inputStream.read();
            }
            inputStream.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return byteArrayOutputStream.toString();
    }

    // Go Back
    @Override
    public void onBackPressed() {

        super.finish();
        if (Animation_Sett == true) {
            // Fading Transition Effect
            TutorialViewActivity.this.overridePendingTransition(
                    android.R.anim.fade_in, android.R.anim.fade_out);
        }

    }// END GO BACK

}

日志错误：

08-08 12:53:18.986: E/AndroidRuntime(4312): FATAL EXCEPTION: main
08-08 12:53:18.986: E/AndroidRuntime(4312): java.lang.NullPointerException
08-08 12:53:18.986: E/AndroidRuntime(4312):     at com.danaraddi.androidtutorial.TutorialViewActivity.onMenuItemSelected(TutorialViewActivity.java:233)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at com.actionbarsherlock.ActionBarSherlock.callbackOptionsItemSelected(ActionBarSherlock.java:604)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at com.actionbarsherlock.internal.ActionBarSherlockNative.dispatchOptionsItemSelected(ActionBarSherlockNative.java:92)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at com.actionbarsherlock.app.SherlockActivity.onOptionsItemSelected(SherlockActivity.java:159)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at android.app.Activity.onMenuItemSelected(Activity.java:2548)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:980)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:735)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:149)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:874)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at com.android.internal.view.menu.ActionMenuView.invokeItem(ActionMenuView.java:547)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at com.android.internal.view.menu.ActionMenuItemView.onClick(ActionMenuItemView.java:115)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at android.view.View.performClick(View.java:4202)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at android.view.View$PerformClick.run(View.java:17340)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at android.os.Handler.handleCallback(Handler.java:725)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at android.os.Handler.dispatchMessage(Handler.java:92)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at android.os.Looper.loop(Looper.java:137)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at android.app.ActivityThread.main(ActivityThread.java:5039)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at java.lang.reflect.Method.invokeNative(Native Method)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at java.lang.reflect.Method.invoke(Method.java:511)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
08-08 12:53:18.986: E/AndroidRuntime(4312):     at dalvik.system.NativeStart.main(Native Method)

教程视图布局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/LinearLayout01"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
   >

    <WebView
        android:id="@+id/TutorialWebView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:paddingLeft="10dp" />
</LinearLayout>
4

1 回答 1

0

好的，

在 tutorialview() 你定位你的 xml 标签 WebView android:id="@+id/TutorialWebView" as wv，然后覆盖它并创建一个新的。并将屏幕设置为此。

然后，当您尝试再次找到它时，它会显示为 null，因为您的新 webview 没有 id。

在 中tutorialview()，注释掉您的新 webview 创建。

 // webview
    WebView wv = (WebView) findViewById(R.id.TutorialWebView);

    // webview settings
    WebSettings webSettings = wv.getSettings();

    // if (Orientation_Sett.equals("Portrait")) {
    // new webview

        //   wv = new WebView(this);   *<---comment this line out (has no id set either)*

  // contentview of webview for progressdialog
    setContentView(wv);

或者

更改您的案例切换块并删除 findviewbyid 行，如下所示

案例 R.id.next：

        TutorialNo++;
        // Loading file html link
        URL = "file:///android_asset/Tutorials/" + TutorialNo
                + "/androidtutorial.html";
        // method called for tutorialview
        //tutorialview();
       // *delete this line*            WebView wv = (WebView) findViewById(R.id.TutorialWebView);

        wv.loadUrl(URL);
        // also DONT use   getApplicationContext() for toasts,  use your activity (this)
        Toast.makeText(this, "Next", Toast.LENGTH_SHORT).show();
    }
于 2013-08-08T13:29:09.880 回答